This invention relates to a dental post system for retaining a dental restoration onto a prepared tooth stub, and more particularly to a contoured dental post which more suitably accommodates the actual shape of the tooth canal in the tooth stub.
In the restoration of devitalized dentition, it is a well known practice to utilize a dental post for retaining a superstructure onto a tooth stub. Typically, the tooth stub is prepared by cutting down the damaged tooth to provide a suitable surface, and then drilling a desired depth into the apical canal to provide an enlarged bore for receiving the dental post. The dental post is then inserted and cemented in the bore. An appropriate core is provided or built up on an upper portion of the dental post, and dental restorative material is used to build a superstructure on the core.
Typically, dental posts heretofore utilized have a generally circular cross section. In preparing the tooth stub to receive such dental posts, circular drill bits are utilized to pre-drill the canal to form a circular bore. The dental posts are then inserted into these bores. However, the actual canal in the tooth stub does not have a circular shape, especially at the upper part thereof, where the canal tends to flare outwardly and often approaches an oval shape.
While it would be possible to drill the canal wide enough to encompass the flared upper portion in order to change the oval shape into a circular shape, this would tend to destroy healthy dentition and weaken the existing tooth stub. As a result, prior art practice has been to drill out the canal using only that size of drill bit which is adequate enough to receive the dental post. Cement was then inserted into those portions of the canal that were larger than the drilled bore so that the cement filled in the gaps between the inserted dental post and the existing canal shape.
The use of such cement to fill in the disparity between the post and the actual canal shape caused problems after the restoration was built up. The cement had a tendency to loosen, permitting the dental restoration to move with respect to the tooth stub. Such movement permits entry of contaminants and decay between the dental restoration and the tooth stub, and may even cause the dental post to be dislodged from the canal, thus requiring replacement of the restoration.
In the co-pending parent application there was provided a solution to this problem by providing a dental post having a contoured periphery to correspond with the oval shape at the mouth of the canal. The dental post included a pair of diametrically opposed, radially projecting ribs which extended longitudinally along at least a portion of the pin. The ribs were suitable to approximate the oval shape of the canal in the tooth stub.
While the ribs provided for such approximation to the oval shape in the width of the canal, the shape of the ribs had substantially longitudinal outer edges with a rather dramatic rounded lower edge. The actual shape at the upper part of the canal is not only oval in width, but is also conical in depth. Accordingly, the presence of the ribs were useful but still did not fully approximate the conical shape and excess healthy dentition had to be removed in order to accommodate the shape of the ribs. SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a dental post which avoids the aforementioned problems of prior art dental posts.
Another object of the present invention is to provide a dental post with a contour which is better suited to approximate not only the actual oval shape of the canal's width, but also to closer approximation the depth of the canal.
Another object of the present invention is to provide to a dental post having a substantially cylindrical body portion with laterally extending contouring means which serve to contour the post both in the lateral and longitudinal directions to approximate the oval cross section and the tapered longitudinal section of a tooth canal.
A further object of the present invention is to provide a dental jig for use in providing a suitable contour shape to a bore in the tooth stub which approximates the tooth canal both in its planar cross section and its vertical cross section.
Briefly, in accordance with the present invention, there is provided a dental post for retaining a dental restoration onto a prepared tooth stub. The dental post includes a cylindrical body portion with appropriate anchoring means for securing the post within a prepared bore formed in the tooth stub. At least one downwardly tapered rib radially projects from the body portion. The rib extends longitudinally along at least a portion of the length of the body portion. The presence of the rib provides a somewhat oval cross sectional shape corresponding to the cross sectional oval shape of the canal in the tooth stub. It also provides a somewhat conically tapered vertical section which again approximates the conical shape of the canal in the tooth stub. Accordingly, a minimum amount of healthy dentition is removed in the formation of the bore.
In a preferred embodiment of the present invention, there is provided a pair of diametrically opposed radially projecting ribs, both of which are downwardly tapered. One of the ribs being shorter than the other.
The present invention also contemplates a dental drill jig for contouring a predrilled bore in the tooth stub to closely approximate the shape of the canal. Such contoured shape will then best accommodate the contoured pin previously described. The dental jig includes a head block from which depends an elongated shaft. The shaft can be inserted into the predrilled bore initially formed through the canal of the tooth stub. At least one offset aperture is provided in the drill jig. The offset aperture includes angled side walls which pass through the head block. The angled aperture continues along the shaft forming an angular aperture along at least a portion of the length of the shaft with the aperture in the shaft being opened.
The aforementioned objects, features and advantages of the present invention will, in part, be pointed out with particularity, and will, in part, become obvious from the following more detailed description of the present invention taken in conjunction with the accompanying drawings, which form an integral part thereof.